A known vehicle body reinforcement unit is disclosed in JP05-116648A which will be hereinafter referred to as Reference 1. The vehicle body reinforcement unit disclosed in Reference 1 includes right and left side members constituting a vehicle body frame and a suspension cross member connecting the right and left side members each other. The aforementioned vehicle body reinforcement unit also includes right and left reinforcement members (i.e., braces). One end of each of the reinforcement members is connected and fixed to a center portion of the suspension cross member in a right-left direction. The other end of each of the reinforcement members is connected and fixed to each of the corresponding side members.
In the vehicle body reinforcement unit disclosed in Reference 1, an iron pipe member of which opposed ends are crushed to form flange portions constitutes each of the reinforcement members (i.e., the braces). One end of each of the reinforcement members is fixed by a bolt to the suspension cross member while the other end of the reinforcement member is fixed by a bolt to the corresponding side member.
A known vehicle body reinforcement unit is also disclosed in WO2006/090586A1 which will be hereinafter referred to as Reference 2. The vehicle body reinforcement unit disclosed in Reference 2 includes a reinforcement member (i.e., a reinforcement apparatus for a vehicle body), which is provided to be removable, along a side frame that extends in a front-rear direction in a vehicle body frame in a state where a longitudinal direction of the reinforcement member coincides with the font-rear direction.
The reinforcement member disclosed in Reference 2 includes a piston that is movable within a hydraulic cylinder and a piston rod provided at the piston. Oil is filled within the hydraulic cylinder so that a flow of oil is restricted or regulated in a case where the piston is operated to expand and contract a volume of the hydraulic cylinder, which leads to generation of a damping force. An outer end portion of the hydraulic cylinder of the reinforcement member including the aforementioned configuration and an end portion of the piston are connected to a predetermined frame of the vehicle body so as to generate the damping force.
According to the vehicle body reinforcement unit disclosed in Reference 1, each of the reinforcement members includes a simple configuration, which may lead to a reduced cost for achieving reinforcement of the vehicle body and to an easy mounting and removing. On the other hand, a function for damping vibration of the vehicle body is not provided.
In addition, according to the vehicle body reinforcement unit disclosed in Reference 2, a force may be generated for restraining expansion and contraction operation of the piston rod (the piston) within the hydraulic cylinder of the reinforcement member. That is, the vehicle body reinforcement unit disclosed in Reference 2 includes a function for retraining vibration of the vehicle body, which improves a vehicle ride quality. In addition, according to the vehicle body reinforcement unit disclosed in Reference 2, opposed end portions of the reinforcement member are provided at an outer side of the vehicle body frame (i.e., monocoque body) to face a road surface. That is, the mounting and removing of the reinforcement member by a user is considered. Nevertheless, a large number of components of the reinforcement unit may increase cost and decrease general versatility.
A vehicle body frame of a passenger vehicle (vehicle), which includes a predetermined rigidity, is expected to improve ride quality depending on one's taste by including the reinforcement member. It is desirable for the reinforcement member mounted to the vehicle to ease impact caused by possible external force applied to the vehicle body frame and restrain vibration at the vehicle body in addition to improving rigidity of the vehicle body frame. Further, in a case where the reinforcement member is provided, the reinforcement member may be mounted to an outer side or a bottom side of the vehicle body frame so as not to decrease maintainability or occupant comfort, for example.
A need thus exists for a vehicle body reinforcement unit which is not susceptible to the drawback mentioned above.